Due to the large number of vehicles on our roads, intense local traffic flows occur now and then. The congestion is particularly noticeable in cities with many intersections, and traffic lights are often adapted to control traffic for optimising the traffic flow.
In some situations it may be appropriate to give priority to specific vehicles, such as emergency vehicles and local public transport. To give these specific vehicles the right of way when passing traffic lights, it is generally known to use signal priority systems. Traffic lights are controlled to give priority to the specific vehicles and to interrupt the normal signal operations. Effective signal priority operations include not only resetting the traffic lights concerned well in advance to allow the specific vehicle to pass, but also timing the operations to reduce disruption of normal traffic to a minimum.
Signal priority systems are disclosed, for example, in U.S. Pat. No. 6,940,422; U.S. Pat. No. 5,926,113; U.S. Pat. No. 6,909,380; and in WO2005/029467. The systems according to the above patents handle signal priority control in different ways, but with the same objective, namely to give the best possible signal priority treatment to one or more specific vehicles. Even if the systems provide increased accessibility for specific vehicles, more could be done in terms of improving the accuracy in identifying which traffic signals will be affected, when they will be affected and how their signals will be manipulated. In other words, there is a need for a solution offering improved advance planning and greater accuracy as to the planned route of the specific vehicle.